Why battleship-style armour does not solve the missile threat

Could sensible external armour make modern warships resistant to anti-ship missiles?

Only at disproportionate cost; localized internal armour, subdivision, damage control, active defenses, and stealth offer more useful protection than a battleship-style belt.

Early anti-ship weapons were designed to attack capital ships. The cited examples are the seven-ton P-700 Granit at about Mach 2.5 and the three-ton BrahMos with a 300-kilogram warhead at about Mach 3. Their size, speed, explosives, and shaped charges make comparison with an unarmed aircraft impact misleading. External armour also cannot readily protect radar, communications, and other exposed systems. Tank-style countermeasures would enlarge a ship's radar return against an uncluttered sea background. The Kirov class instead uses local protection around reactor spaces, while modern survivability depends on avoiding hits, subdivision, redundancy, internal armour, and damage control. Deck-mounted missiles can accept improved weapons more easily than a hull can be rebuilt around a heavy armour scheme, allowing the attack to evolve faster than the armour.